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In the present investigation, we employ a new technique to find several first and second order differential subordination implications involving the following starlike class associated with a bean shaped domain: \begin{equation*}…

Complex Variables · Mathematics 2025-04-24 S. Sivaprasad Kumar , Pooja Yadav

In this article we consider functions $f$ meromorphic in the unit disk. We give an elementary proof for a condition that is sufficient for the univalence of such functions. This condition simplifies and generalizes known conditions. We…

Complex Variables · Mathematics 2017-04-27 Saminathan Ponnusamy , Karl-Joachim Wirths

For every countable ordinal number $\alpha$ we construct an entire function $f=f_\alpha$ such that the family $\left\{f(nz):n\in\mathbb{N}\right\}$ is exactly $Q_\alpha$-normal in the unit disk.

Complex Variables · Mathematics 2010-10-25 Shai Gul , Shahar Nevo

We give some coefficient bounds and distortion theorems for a subclass of univalent functions in the unit disk, and defined using the S\^{a}l\^{a}gean differential operator. The results generalize and unify some well known results for…

Complex Variables · Mathematics 2012-10-08 Ben Ntatin

The aim of this paper is to establish some properties of solutions to the Dirichlet-Neumann problem: $(\partial_z\partial_{\overline{z}})^2 w=g$ in the unit disc $\ID$, $w=\gamma_0$ and…

Complex Variables · Mathematics 2021-03-17 Peijin Li , Qinghong Luo , Saminathan Ponnusamy

Let $Co(\alpha)$ denote the class of concave univalent functions in the unit disk $\ID$. Each function $f\in Co(\alpha)$ maps the unit disk $\ID$ onto the complement of an unbounded convex set. In this paper we find the exact disk of…

Complex Variables · Mathematics 2010-08-31 B. Bhowmik , S. Ponnusamy , K-J. Wirths

In the present work we study solutions of the problem $-(-\Delta)^{\alpha/2}u = f(x,u)$ in $D_0\setminus \overline{D}_1$, with exterior conditions $u = 0$ in $R^N \setminus D_0$ and $u = 1$ in $\overline{D}_1$, where $D_1, D_0 \subset R^N$…

Analysis of PDEs · Mathematics 2018-04-30 Sven Jarohs , Tadeusz Kulczycki , Paolo Salani

n this article we consider functions meromorphic in the unit disk. We give an elementary proof for a condition that is sufficient for the univalence of such functions which also contains some known results. We include few open problems for…

Complex Variables · Mathematics 2019-05-07 See Keong Lee , Saminathan Ponnusamy , Karl-Joachim Wirths

Let $\mathcal{A}$ be the family of functions $f(z)=z+a_2z^2+...$ which are analytic in the open unit disc $\mathbb{D}=\{z: |z|<1 \}$, and denote by $\pe$ of functions $p(z)=z+p_1z+p_2z^2+...$ analytic in $\de$ such that $p(z)$ is in $\pe$…

Complex Variables · Mathematics 2017-05-04 Yaşar Polatoğlu , Yasemin Kahramaner , Arzu Yemişçi Şen

The article discusses criteria for univalence of analytic functions in the unit disc. Various families of analytic functions depending on real parameters are considered. A unified method for creating new sets of conditions ensuring…

Complex Variables · Mathematics 2013-03-06 D. Aharonov , U. Elias

For analytic functions p(z) in the open unit disk U with p(0)=1, Nunokwa has given a result which called Nunokawa lemma (Proc. Japan Acad., Ser. A 68 (1992)). By studying Nunokawa lemma, we obtain this expansion. In this paper, we introduce…

Complex Variables · Mathematics 2013-02-28 Hitoshi Shiraishi , Mamoru Nunokawa

The theory of first-order differential subordination developed by Miller and Mocanu was recently extended to functions with fixed initial coefficient by R. M. Ali, S. Nagpal and V. Ravichandran [Second-order differential subordination for…

Complex Variables · Mathematics 2012-12-20 Lee See Keong , V. Ravichandran , Shamani Supramaniam

In 2001, M.Rekos described the analytic behavior for a function $f(z)$ connected with the Euler totient function for Im$z > 0$ (see (1.2)) imitating the previous research of [1] and [3]. In the present paper, for Im$z > 0$ we describe the…

Number Theory · Mathematics 2024-10-23 Hideto Iwata

For a second order linear differential equation $f''+A(z)f'+B(z)f=0$, with $ A(z)$ and $B(z)$ being transcendental entire functions under some restriction, we have established that all non-trivial solutions are of infinite order. In…

Complex Variables · Mathematics 2020-07-29 Manisha Saini , Sanjay Kumar

In 2002 A.\ Hartmann and X.\ Massaneda obtained necessary and sufficient conditions for interpolation sequences for classes of analytic functions in the unit disc such that $\log M(r,f)=O((1-r)^{-\rho})$, $0<r<1$, $\rho \in (0 , +\infty)$,…

Complex Variables · Mathematics 2014-01-07 Igor Chyzhykov , Iryna Sheparovych

Let $f(z)=\sum_{n=0}^{+\infty} a_nz^n$\ $(z\in\mathbb{C})$\ be an analytic function in the unit disk and $f_t$ be an analytic function of the form $f_t(z)=\sum_{n=0}^{+\infty} a_ne^{i\theta_nt}z^n,$ where $t\in\mathbb{R},$…

Complex Variables · Mathematics 2012-06-19 A. O. Kuryliak , O. B. Skaskiv , I. E. Chyzhykov

Let $f$ be a holomorphic function on the strip $\{z\in C: -\alpha<Im z<\alpha\}, \alpha > 0$, belonging to the class $H(\alpha,-\alpha;\epsilon)$ defined below. It is shown that there exist holomorphic functions $w_1$ on $\{z\in C: 0<Im z…

Complex Variables · Mathematics 2007-05-23 Konrad Schmuedgen

For normalized harmonic functions $f(z)=h(z)+\bar{g(z)}$ in the open unit disk $\mathbb{U}$, a sufficient condition on $h(z)$ for $f(z)$ to be $p$-valent in $\mathbb{U}$ is discussed. Moreover, some interesting examples and images of $f(z)$…

Complex Variables · Mathematics 2013-09-19 Toshio Hayami

This paper consists of three parts: First, letting $b_1(z)$, $b_2(z)$, $p_1(z)$ and $p_2(z)$ be nonzero polynomials such that $p_1(z)$ and $p_2(z)$ have the same degree $k\geq 1$ and distinct leading coefficients $1$ and $\alpha$,…

Complex Variables · Mathematics 2022-11-15 Yueyang Zhang

Let $f$ be function that is analytic in the unit disk ${\mathbb D}=\{z:|z|<1\}$, normalized such that $f(0)=f'(0)-1=0$, i.e., of type $f(z)=z+\sum_{n=2}^{\infty} a_n z^n$. If additionally, \[ \left| \left(\frac{z}{f(z)}\right)^2 f'(z)…

Complex Variables · Mathematics 2021-04-23 Milutin Obradović , Nikola Tuneski